In recent years, compactness and high output have been required in rotary electric machines such as electric motors or generators. With regard to downsizing rotary electric machines of this kind, stator windings that have concentrated windings in which conductor wires are wound onto individual stator core teeth have been used with a view to downsizing coil ends that do not generate effective magnetic flux. However, stators that use stator windings of distributed winding construction that can suppress torque pulsation and increase output are also in demand. In addition, because heat generated in stator windings increases together with increases in output, there is demand for improved cooling of stator windings.
Now, in contrast to concentrated windings, which are configured by winding conductor wires onto individual teeth, windings that are configured by winding conductor wires into slots that are separated by two or more slots are called “distributed windings”. In other words, distributed windings are wound such that a conductor wire that extends outward from one slot spans two or more consecutive teeth and enters another slot.
In conventional rotary electric machines, distributed-winding stator windings have been produced by inserting conductor segments that are formed into a U shape in which end portions of a pair of rectilinear portions are linked together by a return portion from a first axial end of a stator core into respective pairs of slots that are separated by a pitch of one pole and joining together end portions of the conductor segments that extend outward at a second axial end of the stator core, and the stator windings have been cooled by supplying a liquid coolant to coil ends of the stator winding from vertically above (see Patent Literature 1 and 2, for example).